<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .xiaomi {
            position: relative;
            height: 300px;
            width: 500px;
            background-color: pink;
        }

        .box {
            position: absolute;
            right: -220px;
            top: 50%;
            height: 0;
            width: 0;
            border: 20px solid transparent;
            border-left: 200px solid pink;
        }
    </style>
</head>

<body>
    <div class="xiaomi">
        <div class="box"></div>
    </div>
</body>

</html>